The bandwidth of a television signal is a function of the spatial (horizontal, vertical) and temporal resolution to be contained in the signal. As increased resolution is desired in either the vertical, horizontal or temporal directions, the bandwidth of the signal must be increased. High definition television (HDTV) signals contain considerably more resolution than, for example, standard NTSC encoded signals. As a result, various ways have been proposed to generate and transmit HDTV signals, some of which are compatible to a greater or lesser degree with NTSC receivers.
U.S. Pat. No. 4,694,338 describes a system for transmitting an HDTV signal using two separate signals, one of which is fully compatible with existing NTSC receiving equipment and the other containing enhancement information which, when combined with the NTSC compatible signal in a specially designed receiver, reassembles the HDTV signal.
U.S. patent application Ser. No. 246,490, filed Sept. 19, 1988 (a divisional of Ser. No. 931,756), describes an apparatus for encoding HDTV signals of different formats, both progressive and interlaced, as time multiplexed analog components (MAC) multiplexed onto a line having a period which equals a single NTSC line (i.e. 63.555 usec.)
U.S. patent application Ser. No. 077,557 describes a high definition MAC transmission format comprising a signal which is time multiplexed on a line having a period which equals that of two NTSC lines, i.e. 127.11 usec. (referred to as a "superline"). This transmission format is referred to hereinafter as "HDMAC-60" and is designed to be used both as a master feeder signal between program origination and signal redistribution points (e.g. a terrestrial broadcast station and CATV headends), and a signal for DBS (direct broadcast satellite). One feature of the HDMAC-60 format is that it is easily transcoded to NTSC wherever it is necessary within the emission and consumer environments.
The '557 application describes HDMAC-60 encoding and decoding equipment for use with a source signal which is progressively scanned with a 59.94 Hz. frame rate featuring 525 lines in each field and a 16:9 aspect ratio. Although the HDMAC-60 signal can carry video information with a spatial resolution of at least 480 TV lines/picture height (TVL/PH) in the vertical direction and 495 TVL/PH resolution in the horizontal direction if derived from a high line rate studio signal such as 1050 lines, 2:1 interlaced, a system for encoding, transmitting and decoding such a signal using the HDMAC-60 line format, so as to accurately recreate the high definition 1050 2:1 source signal at the receiver, has not been described heretofore.
It is an object therefore of the instant invention, to provide a system for encoding a multiline interlaced signal, for example 1050 lines, 2:1 interlaced, using the HDMAC-60superline format, and decoding it after transmission so as to provide a high definition 1050, 2:1 interlaced signal at a HDTV receiver.